Universal urethane die assembly and method of and apparatus for using same

ABSTRACT

A universal urethane die assembly for use in blanking, forming, drawing, embossing and the like. The assembly includes a urethane pressure pad which is rectangularly shaped with rounded corners. The retaining ring which surrounds and supports the pressure pad has unique dimensional requirements. Other features of the die assembly include a visual indicator for ascertaining the degree of deflection of the die assembly. Also included is a turret punch press which has a single urethane die assembly in lieu of an upper turret. A punching unit which includes a urethane die assembly in conjunction with a die button for use on presses and press brakes.

United States Patent Achler et a1.

[ UNIVERSAL URETHANE DIE Aug. 15, 1972 2,308,998 1/ 1943 Misfeldt ..72/55 ASSEMBLY AND METHOD OF AND APPARATUS FOR USING S AME FOREIGN PATENTS OR APPLICATIONS [72] Inventors: Howard s. Achler, 1348 Berry 199,463 9/1958 Austria ..83/542 Lane, Flossmoor, 111. 60422; Harold Kaufmann, 1919 6th Ave. N.E., Pnma'y Exafmner Frank Rochester Minn- 55901 Attorney-Hill, Sherman, Merom, Gross & Simpson [22] Filed: Sept. 21, 1970 [57] ABSTRACT [21] Appl. No.: 73,859 A universal urethane die assembly for use in blanking,

forming, drawing, embossing and the like. The assembly includes a urethane pressure pad which is [52] 5) rectangularly shaped with rounded corners. The [51] Int Cl B26d 7/26 retaining ring \VhlCh surrounds and supports the pres- [58] Fie'ld 382 374 sure pad has unique dimensional requirements. Other 684 6 features of the die assembly include a visual indicator for ascertaining the degree of deflection of the die assembly. Also included is a turret punch press which [56] Referenm Cited has a single urethane die assembly in lieu of an upper UNITED STATES NT turret. A punching unit which includes a urethane die 2 055 077 9/1936 G 3/ assembly in conjunction with a die button for use on 116F111 d b ak 2,133,445 10/1938 Guerin ..83/21 x presses press r es 2,377,664 6/ 1945 Berger ..72/55 17 Claims, 17 Drawing Figures I ,7 a W f L. iii .2 2/

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SHEET 3 0F 4 UNIVERSAL URETHANE DIE ASSEMBLY AND METHOD OF AND APPARATUS FOR USING SAME BACKGROUND OF THE INVENTION Conventional dies utilized in metal fabrication operations such as blanking, forming and drawing have included a metal male die and a metal female die. The workpiece or blank is inserted between the male and female die members which are then forced together to sever that portion of the workpiece within the confines of the dies. The cutting edge of the male die is slightly undersized with respect to the cutting edge of the female die and as the male die is urged toward the female die the cutting edge of the female die generally penetrates a distance into the workpiece and after such penetration, which causes a cutting action on the workpiece, the remaining thickness of the workpiece fractures or breaks away to completely sever the die-confining portion of the workpiece from the remainder thereof.

The aforementioned conventional die arrangements require close tolerances in the male and female die members. Furthermore, both the male and female die members are subject to wear and thus require periodic replacement.

In recent years urethane die assemblies have been advantageously utilized, in conjunction with a metal die, in performing blanking, forming and drawing operations. In this latter arrangement the urethane die assembly may perform either as a male die, a female die or a compound die and operates in conjunction with a cooperating metal die. Urethane die assemblies do not have to be matched exactly with their corresponding metal die members, can be utilized in a variety of appli cations and have a much longer useful life than do metal die members. For this reason they have come into relatively wide usage in recent years.

Certain problems and difliculties have been observed, however, in the use of urethane die assemblies. Those that are commercially available are often incapable of repeated usage under design loads due to structural failure of the metal retaining ring which surrounds the urethane pressure pad. Such failure has reduced the thickness of the workpiece which can be effectively fabricated with urethane die assemblies. Furthermore, instances have been observed when the die assemblies have been utilized in punch presses or press brakes having a ram force beyond the capabilities of the die assembly, thus causing excessive deflection of the die assembly and rupture or other structural failure of components.

Furthermore, urethane die assemblies have heretofore been utilized generally only on presses and press brakes and have therefore not enjoyed even wider application.

SUMMARY OF THE INVENTION The invention may be summarized generally as comprising an improved universal urethane die assembly and a method of and apparatus for using the same.

More particularly, the die assembly comprises a urethane pressure pad, a pad retaining ring, plunger means including a pressure plate disposed in spaced relation to the retaining ring and compression spring means interposed between the pressure plate and the retaining ring and comprising a plurality of individual urethane spring members disposed in radially angularly spaced relation about the axis of the retaining ring.

Other features of a die assembly constructed in accordance with the principles of the present invention include indicator means for visually indicating the point of maximum operating deflection of the die as sembly, a rectangularly-shaped urethane pressure pad with rounded corners to enhance the applicability of the die assembly and means including a circular The ambit of the present invention also comprises a turret punch press comprising a lower turret mounted for rotation, a universal urethane die assembly and means for mounting the die assembly above the lower turret for reciprocal movement and for applying a ram force to the die assembly.

The invention also comprises a method of punching holes of various shapes in a sheet-form workpiece comprising the steps of positioning in the lower turret of a turret punch press and a plurality of dies corresponding to the various shapes to be punched in the workpiece, positioning above the lower turret for reciprocal movement on a stationary vertical axis a universal urethane die assembly, inserting the workpiece below the lower turret and the urethane die assembly and moving the workpiece and rotating the lower turret to selected positions to align the respective dies with the respective workpiece positions, and lowering the die assembly into punching engagement with "the workpiece as the workpiece and the lower turret are moved and rotated between their respective positions.

The invention also comprises a hole punching unit for use on a punch press, press brake or the like comprising a pair of die holders, a die button mounted on one of the holders and a urethane. die assembly mounted on the other of said holders and comprising an axial urethane pressure pad, a retaining ring surrounding and radially supporting the pressure pad, a pressure plate above the retaining ring, a plunger between the pressure plate and the pressure pad, a urethane spring between said retaining ring and said pressure plate, a punch stem reciprocally carried on said other of said holders and means connecting said retaining ring, said plunger,.said pressure plate, said urethane spring and said punch stem in assembled relation.

Objects of the present invention are to provide a universal urethane die assembly having greater operating load characteristics, to increase the number of ap plications in which urethane die assemblies can be advantageously utilized, and to provide an improved turret punch press and an improved punching unit.

Many other features, advantages and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings, in which preferred structural embodiments incorporating the principles of the present invention are shown by way of illustrative example only.

BRIEF DESCRIPTION OF THE DRAWING FIG. 2 is similar to FIG. 1 but discloses another embodiment of the die assembly with certain parts removed.

FIG. 3 is an enlarged fragmental cross-sectional view of a portion of a urethane die assembly constructed in accordance with the principles of the invention and having means thereon for visually indicating the point of maximum operating deflection.

FIG. 4 is an elevational view taken along lines IV- IV of FIG. 3.

FIGS. 5-8 are similar to FIG. 3 but disclose other embodiments of the visual indication means.

FIGS. 9 and 10 are elevational views of other embodiments of visual indication means.

FIG. 11 discloses a universal urethane die assembly constructed in accordance with the present invention mounted on a turret punch press.

FIG. 12 is a plan view of the die assembly shown in FIGS. 1 and 11.

FIG. 13 is a plan view of a typical sheet-form workpiece which has been formed, punched and notched by virtue of the universal urethane die assembly of the present invention.

FIG. 14 is a perspective view of an improved punching unit constructed in accordance with the principles of the present invention.

FIG. 15 is an enlarged cross-sectional view taken along lines XVXV of FIG. 14.

FIG. 16 is a cross-sectional view of a punching unit constructed in accordance with the present invention.

FIG. 17 is another embodiment of a die button used in connection with a blanking unit shown in FIG. 16.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the perspective view of FIG. 1 and plan view of FIG. 12, a universal urethane die assembly constructed in accordance with the principles of the present invention is indicated generally at reference numeral 10. As will be understood by those skilled in the art, the die assembly 10 can be utilized in the manner of a male die, a female die or a compound die, depending upon whether, in conjunction .with a metal die member, it is performing a punching function, a forming function or a drawing or embossing function.

The die assembly 10 may be more particularly characterized as comprising a urethane pressure pad 11 which is surrounded by a pad retaining ring 12. An outer wall 13 of the pressure pad 11 conforms to an inner wall 14 of the retaining ring 12 and the walls 13 and 14 engage one another in interference fit.

The assembly 10 is of generally axial configuration in that it has a central axis which is disposed vertically in the position of the die assembly 10 shown in FIG. 1. Disposed above the pressure pad 11 is a plunger mechanism 16 which comprises a pressure plate 17, a backup plate 18 and a plunger plate 19.

The pressure pad 11 and the plunger plate 19 both reside within the bore formed by the inner wall 14 of the retaining ring 12 and are similarly shaped to conform to the shape of the bore wall 14. The backup plate 18, on the other hand, is circularly shaped and is disposed generally above an upper wall 20 of the retaining ring 12. The diameter of the backup plate 18, however, is such as to enable the backup plate to be depressed downwardly into the interior of the retaining ring 12 during operation and deflection of the assembly 10 under load.

The pressure plate 17 overlies the backup plate 18 and extends radially outwardly beyond the inner wall 14 of the retaining ring 12. The pressure plate 17 is connected in fixed assembly to the backup plate 18 by means of a threaded bolt 21 and the backup plate 18 is also connected to the plunger plate 19 by suitable means such as threaded bolts or the like.

Disposed between a bottom wall 22 of the pressure plate 17 and the top wall 20 of the retaining ring 12 is a urethane spring member 23 which, in the embodiment thereof shown in FIG. 1, comprises an annularly shaped circumferentially continuous member, a lower portion 23a of which is disposed radially outwardly of the inner wall 14 of the retaining ring 12 and an upper portion 23b of which projects radially inwardly to engage a peripheral wall 24 of the backup plate 18. By virtue of the upper portion 23b, the urethane spring member 23 is maintained in axial alignment with the other components of the die assembly 10.

The retaining ring 12 is maintained in assembled condition within the assembly 10 by virtue of a circular band 26 which is mounted on the top wall 20 of the retaining ring 12 by virtue of a plurality of fasteners such as the threaded bolts indicated at reference numerals 27. An inner wall 28 of the band 26 conforms in shape to the peripheral wall 24 of the backup plate 18 and thus extends over those comer portions of the pressure pad 11 and the plunger plate 19 which project beyond the periphery of the backup plate 18.

The pressure plate 17 is adapted by bolt holes 29 or other suitable means for connected assembly to the ram of a punch press, press brake or the like.

In operation, the die assembly 10 is used in conjunction with a metal die and the workpiece is inserted between the metal die and the urethane die assembly 10. A ram force is applied to the plunger mechanism 16 and is transmitted from the pressure plate 17, the backup plate 18 and the plunger plate 19 to the urethane pressure pad 11. The pressure pad 11 is forced into engagement with the workpiece and deforms under force to sever the workpiece along a cutting line determined by the metal die.

As a consequence of its deformable, resilient characteristics, however, the urethane pressure pad 11 also applies a radial force on the inner wall 14 of the retaining ring 12. The retaining ring 12 supports the urethane pressure pad 11 against such radial force to permit a high cutting force to be developed on the workpiece by the pressure pad 11.

As noted, the pressure pad 1 1 is rectangularly shaped with rounded corners indicated at reference numeral 30. It has been determined that this generally rectangular shape of the pressure pad 11 enables the die assembly to perform a greater number of punching, forming and drawing operations in fewer strokes than would otherwise be the case were the pressure pad 11 cylindrically shaped in the manner of the backup plate 18.

As the pressure plate 17 transmits the force of the ram through the backup plate 18 and the plunger plate 19 to the pressure pad 11 it also transmits a load through the urethane spring member 23 to the retaining ring 12. By virtue of this arrangement the retaining ring 12 is urged under heavy load into the workpiece around the pressure pad 11 to hold the workpiece stationarily before sufficient pressure is developed on the workpiece by the pressure pad 11 to begin the punching, forming or drawing operation on the workpiece.

FIG. 2 illustrates a die assembly a which is similar to the die assembly 10 shown in FIG. 1 except that the spring means interposed between the pressure plate 17 and the retaining ring 12 comprises a plurality of individual urethane members disposed in radially angularly spaced relation about the axis of the assembly 10a. The individual urethane spring members are indicated at reference numerals 31 and in the embodiment shown in FIG. 2 comprise vertical columns the dimensions of which are such that the diameter thereof is greater than the height. The utilization of the individual urethane spring members 31 enables the effective spring rate between the pressure plate 17 and the retaining ring 12 to be varied simply by varying the height of the columnar members 31.

Prior art universal urethane die assemblies have failed in many instances as a consequence of structural failure of the retaining ring 12 and the inability thereof to adequately support the radial force applied thereto by the pressure pad 11. The present invention includes within its ambit the discovery that the configuration of the retaining ring 12 can be optimized if the radial dimension of the retaining ring 12, that is, the distance between the inner wall 14 and an outer wall 32 thereof, is always greater than the vertical dimension thereof, that is, the distance between the top wall thereof and a bottom wall 33 by a ratio of at least 1.6:l.5. While a ratio of 2:1.5 may be preferable in some instances, a ratio of 1.6: l .5 provides increased load capabilities of the die assembly 10 regardless of the material of which the retaining ring 12 is made (generally, metal) and regardless of the yield strength thereof.

It will be appreciated, however, that the die assembly 10 does have some maximum operating load characteristics and that a vertical ram-force should not be imposed on the assembly 10 or the urethane pressure pad 11 beyond a predetermined level. In order to provide a visual indication of maximum permissible operating deflection the present invention contemplates the utilization of visual indication means which are indicative of the level of deflection.

To that end a band-like indicator member 34 is fastened to an outer peripheral wall 36 of the pressure plate 17 and depends downwardly in the direction of the retaining ring 12. In the unstressed or unloaded condition of the die assembly 10 a bottom edge 37 of the indicator band 34 is disposed in axially spaced relation with respect to the top wall 20 of the retaining ring 12. As the die assembly 10 is loaded to deform the spring member 23 the lower edge 37 of the indicator band 34 is moved closer to the top wall 20 of the retaining ring 12.

The spring member 23 is provided with a radially outwardly and upwardly extending tab 38 which is in axial alignment with the indicator band 34. Preferably the tab 38 is color-coded for ready identification and the outer surface of the band 34 may also receive suitable indicia to enable the operator to quickly and visually determine the extent of deflection of the assembly 10 to ensure that the maximum permissible limit is not exceeded. The tab 38 for example, can be colored yellow and the indicator band 34 can be colored red so that the operator may rapidly apprise himself of the absence or presence of an excessive load on the die assembly 10.

While it is desirable that the die assembly 10 be subjected to no ram loading sufficient to bring the lower edge 37 of the indicator band 34 into abutment with the tab 38, it is noted that the tab is slightly raised above the top wall 20 of the retaining ring 12 to prevent deformation of the indicator band 34 should the maximum load be exceeded.

FIG. 4 is illustrative of the color coding of the indicator band 34 and of the tab 38 and indicates the manner in which the space or gap between the lower edge 37 of the indicator band 34 and the tab 38 is easily recognized. Other suitable indicia such as a warning to avoid excessive deflection may also be provided on the indicator band 34.

FIG. 3 is illustrative of the embodiment of the die assembly 10a shown in FIG. 2 in which the columnar spring members 31 are utilized. In this case the absence of a tab such as the tab 38 of the circumferentially continuous spring member 23 suggests that the spring members 31 themselves should be suitably colored to easily and rapidly provide a visual indication of the degree of deflection of the indicator band 34 toward the top surface 20 of the retaining ring 12.

FIG. 5 discloses indicator means for ascertaining deflection and comprises a pair of band-like members 39 and 40 connected respectively to the pressure plate 17 and the retaining ring 12. The bands 39 and 40 are provided with different colors and other suitable indicia can be provided to readily indicate the degree of deflection.

In some instances, particularly upon failure of the die assembly 10, it is desirable to know whether the maximum permissible degree of deflection has been exceeded. To provide such tell-tale indication the present invention involves several embodiments of indicator means which result in permanent deformation or breakage upon excessive deflection.

For example, the embodiment illustrated in FIG. 6 comprises a plastic band 41 depending downwardly from the pressure plate 17 and a metal band 42 inserted into a groove 43 formed in an enlarged bottom end 44 of the band 41. The material used in constructing the band 41 may be rigid, brittle material so that it will snap and break in the event that the metal band '42 is brought into abutment with the upper surface 20 of the retaining ring 12. Once the band 41 is broken, of course, there exists a permanent indication that the maximum permissible deflection of the die assembly 10 has been exceeded.

FIGS. 7 and 8 also. include indicating means comprising brittle plastic bands 46 and 47 respectively. In these two embodiments the bands are brought directly into engagement with the retaining ring 12 upon development of an excessive load on the die assembly 10 and are constructed and designed so as to experience a permanent rupture when subjected to any substantial compression load.

FIG. 9 discloses another indication means for ascertaining deflection and comprises a pair of arrowhead members 48 and 49 connected in fixed assembly respectively to the pressure plate 17 and to the retaining ring 12. The maximum permissible deflection has been attained when the arrowheads of the two members are in point-to-point alignment with one another.

The indicator means disclosed in FIG. 10 comprises a shear pin 50 extending from the peripheral wall 36 of the pressure plate 17 and in axial alignment with an abutment member 51 mounted on the retaining ring 12. If the load on the die assembly is sufficiently great to cause deflection whereby the shear pin 50 is brought into engagement with an upper arm 52 of the member 51 the shear pin will fail, thus disclosing a permanent tell-tale of excessive deflection.

The present invention also contemplates the provision of an improved turret punch press which utilizes a universal urethane die assembly in lieu of the upper turret.

Referring to FIG. 11, a turret press is indicated generally at reference numeral 53, portions thereof being shown somewhat diagrammatically. The press 53 comprises a lower turret 54 which is mounted for rota tion on a vertical axis by virtue of a rotatable shaft 56. In the embodiment illustrated a plurality of metal dies, one of which is indicated at reference numeral 57, are disposed in angularly spaced relation about the axis of the lower turret 54.

In the embodiment illustrated the metal dies 57 are somewhat disc-shaped. It will be appreciated, however, by those skilled in the art that in many instances the dies of a turret press may more resemble vertical columns and fit into bores provided in the lower turret.

Furthermore, in conventional turret presses there is also provided an upper turret which is rotatable about an axis aligned with the axis of rotation of the lower turret. Generally a plurality of punch dies are mounted in the upper turret in alignment with female dies formed in the lower turret, but of course, such arrangements are subject to a high degree of flexibility in many turret presses.

The turret press 53 differs from those of the prior art, however, in that the upper turret is eliminated and in its stead is a universal urethane die assembly 10 indicated at reference numeral 10 since it may correspond identically with the assembly 10 (shown in FIG. I) mounted on a reciprocal ram 59 by virtue of a tang or the like indicated at reference numeral 59a. The die assembly 10 can be utilized with any of the metal dies mounted on the lower turret 54 and it is not necessary that the die assembly 10 rotate jointly with the lower turret 54 but instead is mounted on a stationary vertical axis for reciprocal movement only.

Thus, instead of the turret press 53 requiring an upper turret with a mating die for each die mounted on the lower turret 54, there is provided only a single universal urethane die assembly 10 which is utilized in association with all of the various dies mounted on the lower turret 54.

It will be appreciated that arrangement of the turret press 53 substantially simplifies the design and construction of the turret press 53 and substantially reduces manufacturing costs but also reduces tooling costs since the only metal dies required are those which are mounted on the lower turret 54. While the turret 54 is referred to herein as a lower turret, it is understood that the press 53 includes only a single turret,

turret 54, and does not include an upper turret in the conventional sense but instead only a single die assembly 10.

A sheet-form workpiece is shown at reference numeral 58 inserted between the die assembly 10 and the metal die 54. In the illustrated embodiment the urethane pressure pad 11 extends horizontally beyond the periphery of the metal die 57, which is used to provide holes 62 in the workpiece 58 by virtue of the pair of holes 60 formed in the metal die 57. The slugs which are cut by the die 57 drop gravitationally through bores 61 extending up to the holes 60.

It will be appreciated, however, that it is not essential to the principles of the present invention that the action surface of the urethane pressure pad 11 extend beyond the action surface of the die 57 since, if the situation is otherwise, it is merely necessary that multiple drops of the die assembly 10 be made as the lower turret 54 is rotated.

Change-over time is also reduced since it is not necessary to change over two sets of dies but only the single set carried by the lower turret 54. Since the urethane die assembly 10 constructed in accordance with the principles of the present invention may be advantageously utilized in blanking, forming and drawing sheet metal, for example, up to 12 gauge, it will be appreciated that the turret press 53 will find utility in many of the applications in which conventional turret presses have heretofore been used.

The present invention also contemplates the utilization of urethane die assemblies in punching units or punch and die assemblies. A punching unit generally comprises a C-shaped frame or die holder. A male die or punch is mounted on one arm of the holder and a female die is mounted on the other arm. Punching units are generally employed with punch presses or press brakes in fabricating limited quantities of blanks. Usually a template is placed on the bed of the press or brake and a plurality of punching units are disposed or indicated on the template with appropriate male and female die members.

Referring to FIGS. 14 and 15 there is disclosed a punching unit in accordance with the principles of the present invention. The punching unit, indicated generally at reference numeral 66, comprises a C- shaped holder 67 including an upper arm 68 and a lower arm 69. Mounted in the lower arm 69 is a die button 70 including a metal die, and an exit slot 71 is formed in the lower arm 69 to enable slugs to drop therethrough.

A urethane die assembly 72 is mounted on the upper arm 68 and comprises a urethane pressure pad 73 which is surrounded by a metal retaining ring 74. A plunger plate 76 resides above the pressure pad 73 and abuts a pressure plate 77 immediately thereabove. A pair of shoulders 78 and 79 are formed respectively on the retaining ring 74 and the plunger plate 76 to prevent axial separating movement therebetween. A urethane spring member 80 is interposed between the pressure plate 77 and the retaining ring 74.

Extending axially upwardly from the pressure plate 77 is a ram stem 81 which is joumalled in a bore 82 fonned in the upper arm 68. The stem 81 is apertured as at 83 to receive a bolt 84 which is threaded into the plunger plate 76 as indicated at reference numeral 86.

An enlarged head 87 of the bolt 84 maintains the entire die 72 in assembled condition. A preloaded spring 88 bottoms on the upper arm 68 and on an upper flange 89 of the ram stem 81 to bias the ram stem upwardly with respect to the upper arm 68.

l-leretofore, as will be understood by those skilled in the art, each punching unit required a pair of complemental metal die members carefully machined to close tolerances. By virtue of the present invention a blanking unit now requires only a single metal die, since the universal urethane die assembly 72 is able to accommodate all metal die members which may be mounted on the lower arm in any punching operation.

In the punching unit indicated generally at reference numeral 90 in FIG. 16 the upper and lower die holders, indicated respectively at 91 and 92, do not form part of a single C-frame. Instead each of the holders 91 and 92 comprises a separate unit so that each can be mounted on a template which utilizes a pair of templates.

The punching unit 90 is similar in many respects to the punching unit 66 in that it comprises a urethane pressure pad indicated at 93 which is surrounded by a retaining ring 94. The ring 94 is carried in a bore 96 of a ram stem 97, which bore 96 also houses a plunger mechanism comprising a plunger rod 98, a backup rod 99 and a pressure rod 100. A ring-shaped urethane spring member 101 is interposed between the pressure rod 100 and the retaining ring 94.

The lower die holder 92 is bored as at 102 to receive a metal die button 103, the slug formed by which drops gravitationally through an exit chute 104. Positioning studs 106 and 107 are carried by the holders 91 and 92 in order to facilitate positioning of the holders on their respective templates. In addition, a plurality of bores as at 108 and 1109 are provided to enable the holders to be fixedly connected to their respective templates by means of suitable threaded bolts or the like.

Another embodiment of the die button 103 is indicated in FIG. 17 at reference numeral 103. The button comprises a metal disc 104 which resides in the bore 105 thereof. A urethane spring member 106 also resides in the bore 105 and after the urethane pressure pad 93 has been applied to the die button to form a slug in the workpiece, spring member 106 and the disc 104 serve to eject the slug from the bore 105 as the pressure pad 93 is retracted.

Although minor modifications might be suggested by those versed in the art, it should be understood that we wish to embody within the scope of the patent warranted hereon all such modifications as reasonably come within the scope of our contribution to the art.

We claim: l. A universal die assembly for blanking, punching, forming or the like comprising a urethane pressure pad, a pad retaining ring, plunger means including a pressure plate disposed in spaced relation to said retaining ring, and

compression spring means interposed between said pressure plate and said retaining ring and comprising a plurality of individual urethane spring members disposed in radially angularly spaced relation about the axis of said retaining ring.

2. The invention as defined in claim 1 wherein said individual urethane spring members are shaped in the form of columns.

3. A universal die assembly comprising an axial urethane pressure pad,

a pad retaining ring surrounding said pad and having inner pad supporting walls engaging the pad in interference fit relation,

plunger means including a pressure plate disposed in spaced relation to said retaining ring, and

compression spring means interposed between said pressure plate and said retaining ring, said pressure pad being substantially rectangularly shaped in radial cross-section.

4. The invention as defined in claim 3 wherein the corners of said pressure pad are rounded in radial cross-section.

5. The invention as defined in claim 3 and including means forming a circular retaining band mounted in fixed assembly on said retaining ring and overlying the comers of said pressure pad for maintaining said retaining ring and said plunger means in assembled relation.

6. A generally axial universal die assembly comprising a urethane pressure pad,

a pad retaining ring surrounding and radially supporting said pressure pad, plunger means for abutting and applying an axial force to said pressure pad including a pressure plate extending radially outwardly in overlying and axially spaced relation with respect to said retaining ring,

compression spring means interposed between said pressure plate and said retaining ring for resisting relative axial movement thereof toward one another, and

indicator means including means carried for joint axial movement on said pressure plate for providing a visual indication of the degree of relative axial movement of said pressure plate and said retaining ring.

7. The invention as defined in claim 6 wherein said spring means comprises a urethane member and said indicator means comprises an indicator band connected to and extending axially from said pressure plate toward said retaining ring, and

means forming a tab on said urethane spring member extending radially outwardly into axial alignment with said indicator band for abutment therewith upon relative axial movement or deflection of said pressure plate and said retaining ring a predetermined distance.

8. The invention as defined in claim 7 and including means forming indicia on said urethane spring member for assisting in providing rapid visual indication of deflection.

9. The invention as defined in claim 7 wherein said tab is normally disposed in axially spaced relation with respect to said retaining ring.

10. The invention as defined in claim 6 wherein said indicator means comprises a pair of arrowhead brackets mounted respectively on said pressure plate and said retaining ring for indicating the degree of deflection thereof.

11. The invention as defined in claim 6 wherein said indicator means comprises a rigidshear pin and a normally axially spaced pin abutment member mounted on said pressure plate and on said retaining ring for providing a permanent indication of excessive deflection.

12. The invention as defined in claim 6 wherein said indicator means comprises a rigid deformable member mounted on said pressure plate and engageable with said retaining ring upon excessive deflection thereof for providing a permanent indication of such excessive deflection.

13. The invention as defined in claim 6 wherein said indicator means comprises a substantially nondeformable, brittle plastic member.

14. A generally axial universal die assembly comprismg a urethane pressure pad,

a centrally apertured pad retaining ring surrounding said'pad,

a plunger assembly for applying an axial force to said pressure pad and including a pressure plate spaced axially from said retaining ring and a circular backup plate adjacent said pressure plate and movable into the aperture of said retaining ring, and

spring means comprising an annularly shaped urethane member interposed between said pressure plate and said retaining ring and axially aligned therewith, said urethane member extending circumferentially continuously around said backup plate and having a first portion spaced radially from said backup plate and a second portion formed integrally with said first portion and extending radially into abutting engagement with the peripheral wall of said backup plate for maintaining axial alignment of said urethane member, said backup plate and said retaining ring.

15. A universal die assembly having a central axis and comprising a urethane pressure 'pad,

a metal retaining ring surrounding said pressure pad,

and

means for applying an axial force to said pressure pad,

said retaining ring comprising a circumferentially continuous hoop-shaped member which is substantially rectangular in radial cross-section and which is dimensioned so that the radial length thereof is always greater than the axial length.

16. The invention as defined in claim 15 wherein said hoop-shaped member is dimensioned so that the ratio of the radial length thereof to axial length is always greater than 1.6: 1.5.

17. The invention as defined in claim 15 wherein said hoop-shaped member is dimensioned so that the ratio of the radial length thereof to axial length is equal to or greater than 2: 1.5.

UNTTED STATES PATENT oTTTcE QERTIWCATE (Ti QQRREQTWN Patent No. 3,683,735 Dated August 15, 1972 Inventor(s) Howard S. Achler and Harold Kaufmann It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

On the page with the Abstract, after the inventors. identification,

insert (73) 'Assignee: Houdaille Industries, Inc., Buffalo, New York.

Signed and sealed this 10th day of April 1973 (SEAL) Attest:

EDWARD M.PLETCHER,JR.

ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents ORM PO-1050 (10-69) USCOMM-DC 60376-P69 n u.s GOVERNMENT PRINTING OFFICE: I969 o-sse-3sa 

1. A universal die assembly for blanking, punching, forming or the like comprising a urethane pressure pad, a pad retaining ring, plunger means including a pressure plate disposed in spaced relation to said retaining ring, and compression spring means interposed between said pressure plate and said retaining ring and comprising a plurality of individual urethane spring members disposed in radially angularly spaced relation about the axis of said retaining ring.
 2. The invention as defined in claim 1 wherein said individual urethane spring members are shaped in the form of columns.
 3. A universal die assembly comprising an axial urethane pressure pad, a pad retaining ring surrounding said pad and having inner pad supporting walls engaging the pad in interference fit relation, plunger means including a pressure plate disposed in spaced relation to said retaining ring, and compression spring means interposed between said pressure plate and said retaining ring, said pressure pad being substantially rectangularly shaped in radial cross-section.
 4. The invention as defined in claim 3 wherein the corners of said pressure pad are rounded in radial cross-section.
 5. The invention as defined in claim 3 and including means forming a circular retaining band mounted in fixed assembly on said retaining ring and overlying the corners of said pressure pad for maintaining said retaining ring and said plunger means in assembled relation.
 6. A generally axial universal die assembly comprising a urethane pressure pad, a pad retaining ring surrounding and radially supporting said pressure pad, plunger means for abutting and applying an axial force to said pressure pad including a pressure plate extending radially outwardly in overlying and axially spaced relation with respect tO said retaining ring, compression spring means interposed between said pressure plate and said retaining ring for resisting relative axial movement thereof toward one another, and indicator means including means carried for joint axial movement on said pressure plate for providing a visual indication of the degree of relative axial movement of said pressure plate and said retaining ring.
 7. The invention as defined in claim 6 wherein said spring means comprises a urethane member and said indicator means comprises an indicator band connected to and extending axially from said pressure plate toward said retaining ring, and means forming a tab on said urethane spring member extending radially outwardly into axial alignment with said indicator band for abutment therewith upon relative axial movement or deflection of said pressure plate and said retaining ring a predetermined distance.
 8. The invention as defined in claim 7 and including means forming indicia on said urethane spring member for assisting in providing rapid visual indication of deflection.
 9. The invention as defined in claim 7 wherein said tab is normally disposed in axially spaced relation with respect to said retaining ring.
 10. The invention as defined in claim 6 wherein said indicator means comprises a pair of arrowhead brackets mounted respectively on said pressure plate and said retaining ring for indicating the degree of deflection thereof.
 11. The invention as defined in claim 6 wherein said indicator means comprises a rigid shear pin and a normally axially spaced pin abutment member mounted on said pressure plate and on said retaining ring for providing a permanent indication of excessive deflection.
 12. The invention as defined in claim 6 wherein said indicator means comprises a rigid deformable member mounted on said pressure plate and engageable with said retaining ring upon excessive deflection thereof for providing a permanent indication of such excessive deflection.
 13. The invention as defined in claim 6 wherein said indicator means comprises a substantially non-deformable, brittle plastic member.
 14. A generally axial universal die assembly comprising a urethane pressure pad, a centrally apertured pad retaining ring surrounding said pad, a plunger assembly for applying an axial force to said pressure pad and including a pressure plate spaced axially from said retaining ring and a circular backup plate adjacent said pressure plate and movable into the aperture of said retaining ring, and spring means comprising an annularly shaped urethane member interposed between said pressure plate and said retaining ring and axially aligned therewith, said urethane member extending circumferentially continuously around said backup plate and having a first portion spaced radially from said backup plate and a second portion formed integrally with said first portion and extending radially into abutting engagement with the peripheral wall of said backup plate for maintaining axial alignment of said urethane member, said backup plate and said retaining ring.
 15. A universal die assembly having a central axis and comprising a urethane pressure pad, a metal retaining ring surrounding said pressure pad, and means for applying an axial force to said pressure pad, said retaining ring comprising a circumferentially continuous hoop-shaped member which is substantially rectangular in radial cross-section and which is dimensioned so that the radial length thereof is always greater than the axial length.
 16. The invention as defined in claim 15 wherein said hoop-shaped member is dimensioned so that the ratio of the radial length thereof to axial length is always greater than 1.6: 1.5.
 17. The invention as defined in claim 15 wherein said hoop-shaped member is dimensioned so that the ratio of the radial length thereof to axial length is equal to or greater than 2:1.5. 